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Why does my 2000 4.7L Dodge Dakota not start?

animeisteranimeister Posts: 6
edited August 2016 in Dodge
We have a 2000 Dodge Dakota 4.7L. The truck cranks but does not start. The fuel pump is new, the injectors are new, and the spark plugs are new. It has good fuel pressure, good spark, and good relays. It gets going with some starter fluid but dies within a second or two. At first we suspected the fuel pump and it was horrible, broken filter, but ultimately, did not resolve the problem. The spark plugs were changed, but still nothing. The injectors were all replaced, but still nothing. All relays and fuses have been tested. ASD relay was replaced and still nothing. Good spark is achieved and good pressure is achieved. What could possibly be wrong with this Dakota?

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Answers

  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    One possibility is that the injectors are not opening. You can test them with a NOID light.
  • We tested the injectors with a NOID light and they are getting power. I'm running out of ideas as to why this truck just isn't starting. We've been at it for about three weeks now.
  • 93tracker5spd93tracker5spd North East Ohio USAPosts: 194
    Hello! Sounds like you have eliminated most things. So at this point I would guess plugged fuel line, either where it feeds the throttle body, or the fuel rails. I admit that it's a stab in the dark, but it sounds like you have covered everything else.
  • We get a fuel pressure reading of 50 PSI to the fuel rail. We had removed them earlier and cleaned them out. We removed them again just now and there's plenty of fuel everywhere. We're checking the actual new injectors we put in for resistance. Would anyone happen to know what resistance they should have?
  • 93tracker5spd93tracker5spd North East Ohio USAPosts: 194
    Hello again! I have found a page with the entire procedure, and the resistance, listed below.

    http://troubleshootmyvehicle.com/chrysler/4.7L/how-to-test-a-bad-fuel-injector-1
  • The injectors are working fine. When we took out the injector rail there was plenty of gas throughout and the ends of the injectors were wet with gas too. Spark plugs work too. It seems like there just isn't any combustion at all. Keep the suggestions coming.
  • 93tracker5spd93tracker5spd North East Ohio USAPosts: 194
    Hello again, you really have a stumper there. It seems as if you have tried everything. I can thank of nothing else in the conventional sense, so I am going to go way out on a limb here, please don't thank I have lost my mind. This being a 2000, it would have an ecu or ecm, you said the original fuel pump was in very bad condition, broken filter and such. The computer that controls fuel air mixture, idle, shift timing, cam timing and so on would have tried to compensate for that condition. Have you tried clearing the computer and letting it start over? If not, un-hook the battery, both cables, and leave overnight, then try to start the engine. If it starts, let it idle for at least 10 minutes, then drive only in town at street speeds for about 20 miles so that it can relearn the settings that will work with this new pump and injectors and so on. Like I said, this is far fetched, but it is a chance. The settings the ecu has now may be shutting out to much air and that would effect weather it starts and idles. Just a wild guess.
  • thecardoc3thecardoc3 Posts: 5,054
    A noid light does not prove that there is enough current flowing to actually command the injectors open. There have been a lot of people misled by trusting them. In order to prove that the injectors are really being commanded open the right tools to use are a multi channel digital oscilloscope and a low amps current probe.

    The scope allows you to measure the supply voltage to the injectors, as well as the computers ability to get the ground command close to 0v. If there is a poor connection, or corrosion in the circuit there will be a voltage drop occurring when the injectors are turned on. The moment they are turned back off and there is no current flowing, the voltage levels return to normal. A voltmeter cannot show you this since because it doesn't update fast enough.

    The low amps current probe will sense the current flowing in the circuit and output a voltage that the scope can display. The resulting waveform is so precise that we can see the pintle in the injector mechanically open in the ramp as the current in the circuit builds.

    Reading back through to double check, I did not see where you tested the fuel to see if it is good or not.
  • We tried removing the battery for a day actually, but it didn't work. As for checking the proper voltage drop at the injectors, we don't have the tools. However, that may be the issue we're facing with this truck. I think at this point we will take it to the dealership to have them run a diagnostics test. It's a bit pricey, but we're almost certain there's a module problem. Any advice?
  • Mr_ShiftrightMr_Shiftright Sonoma, CaliforniaPosts: 64,490
    Have you done a compression test? Have you pulled a spark plug and looked and smelled for fuel residue?

    Starting fluid can trick you--it's so combustible that even the feeblest spark or marginal compression will ignite it.

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